PLATE XXVI. 



PAGE. 



Figs. 1 to 6. BYTHOPORA HERRICKI Ulr 263 



]. Vertical section x]g, showing slight irregularity in the growth. 

 2 and 3. Tangential section xis and a portion of same *50. 

 4 and 5. A large and an average si/ed specimen. 

 6. Surface of the smaller xg. 



Middle third of the Trenton shales at Minneapolis. 



Figs. 7 to 9. BYTHOPORA ALCICORNIS, n. sp 264 



7 and 8. Two specimens of the natural size. 

 9. Surface of the larger one *9. 



Upper third of the Trenton shales near Cannon Falls. 



Figs. 10 tO 16. HOMOTRYPELLA (?) SUBGRACILIS, n. Sp 230 



10 and 11. Two tangential sections xig, showing slight differences. 



12. Vertical section x is.. The structure is almost entirely destroyed and only the direc- 

 tion of the tubes is to be made out with any certainty. 

 13 and 14. Two specimens, the second a little above the average in size. 

 15 and 16. Surface of the larger specimen xg and xis. 

 Middle third of the Trenton shales, St. Paul. 



Figs. 17 to 19. ERIDOTRYPA EXIGUA, n. sp 266 



17. A group of fragments as they appear mounted on a slide. 

 18 and 19. Two of them X9. 



Upper part of the Galena shales near Cannon Falls. 



Figs. 20, 21, 29 and 30. ERIDOTRYPA MUTABILIS, var. MINOR, n. var 266 



20. Three fragments of the natural size . 



21. Surface of one of them xg. 



29 and 30. Vertical and tangential sections xi8. 

 Galena shales near Cannon Falls. 



Figs. 22 to 28, 31, 32. ERIDOTRYPA MUTABILIS, n. sp 265 



22. A specimen of the average size. 



23. Large example. 



24. Surface of an old example presenting an unusual appearance, *18. 



25. Surface of the original of flg. 23, x]8. The figure includes one of the niaculie and ex- 



hibits the most common appearance of these. 



26 and 27. Tangential section x]g and a portion of same X50 ; represents an average fully 

 matured condition. 



28. Vertical section of the same specimen xi8; shows a superficial layer of zocecia growing 

 in a direction opposite to the first set. 



31 and 32. Vertical and tangential sections xis, of an old specimen which has grown irreg- 

 ularly causing many interspaces and thus unusually numerous and large mesopores. 

 Galena shales, Goodhue county, Minn. 



Figs 33 to 37. BATOSTOMA WINCHELLI Ulr 295 



33. A specimen of the usual diameter. 



34. Another, of large though not uncommon size. 



35. An average example of the var. nodosa. 



36. Surface of a fully matured example xg. 



37. Surface of the original of flg. 33 xg and xis. (See also plate 27.) 

 Middle third of the Trenton shales, Minneapolis and St. Paul. 



Figs. 38 to 40, BATOSTOMA MINNESOTENSE, n. sp 297 



38 and 39. Two specimens, the first small, the other of the average size. 

 40. Surface of the larger specimen, which is in an excellent state of preservation, xg, show- 

 ing the granulose walls. (See also plate 27.) 

 Middle third of the Trenton shales, Minneapolis. 



